Filter are commonly used to separate contaminants from a fluid stream passing through a fluid system. Many fluid filters use a filter media which has a structure that traps the contaminants either within the media, or causes the contaminants to collect on the outer surface of the media. In certain applications, for example in some fuel systems, a filter will collect particulate matter and/or water on the outside surface of the filter media. The contaminants will then drain or fall down under gravity to a lower chamber in the filter. A drain assembly is provided in the lower chamber to allow such contaminants to be removed. Some applications also require fluid in the filter to be removed prior to an element change. The drain assembly is also used for this purpose.
Many filters include a collection bowl screwed onto the lower end of the filter can to collect the contaminants. A removable collection bowl generally allows the filter element to be removed and discarded and the collection bowl to be re-used. This reduces cost and material waist. Many of such collection bowls are transparent to allow visual confirmation of the contaminants in the collection bowl. Other filters simply have the chamber integral with a lower end wall of the filter can to collect the contaminants.
A common type of drain assembly for such fluid filters includes a valve cap or knob which can be rotated to open a valve and allow the fluid/contaminants to drain out. Such a drain assembly is shown, for example, in Schaupp, U.S. Pat. No. 4,724,074. The Schaupp patent shows a conventional filter element with a removable collection bowl. Popoff, et al., U.S. Pat. No. 4,740,299; Church, et al., U.S. Pat. No. 4,619,764 and Wilson, et al., U.S. Pat. No. 4,502,956 show similar types of filter elements, with and without separate collection bowls, where a drain assembly is provided for removing fluid and other contaminants from the filter.
Many of such drain assemblies are self-venting, that is, they allow air to enter the filter when the valve is opened. This prevents a vacuum from forming within the filter, and facilitates the rapid out-flow of fluid and contaminants from the filter.
While the above-identified drain assemblies are appropriate for many applications, it is believed that there continues to be a demand for drain assemblies that are low in cost, simple to use, and easy to manufacture and assemble.